1. Field of the Invention
The invention relates to apparatus for automatic suture fixation and methods for minimally invasive cardiac surgery employing such apparatus. In particular, the invention relates to apparatus for automatic suture fixation including a first cylinder fitted with first securing means on its exterior surface and a second cylinder with second securing means on its interior surface, whereby sutures may be secured between these cylinders when the corresponding securing means engage. Further, methods for minimally invasive cardiac surgery employing such apparatus may include the steps of threading the sutures used to secure a replacement heart valve over the exterior surface of the first cylinder and over the interior surface of the second cylinder, applying pressure against the first cylinder to secure it against the replacement valve, and applying tension against the sutures to achieve a blood-tight seal between the replacement valve and the heart, before securing the sutures between the first and second cylinders.
2. Description of Related Art
Current methods of placing replacement heart valves, including prosthetic valves, harvested pig valves, and human donor valves, require the careful placement and tying-off of numerous sutures. In heart valve replacement surgery, a damaged, defective, or diseased heart valve is removed to provide an annulus for securing a replacement valve. In order to prepare the annulus to receive the replacement valve, traction stitches may be placed through the annulus from both the superior and inferior aspects of the annulus. By applying tension to these sutures, the annulus may be better exposed to facilitate positioning of the replacement valve.
Replacement valves may be fitted with a sewing ring, which surrounds the valve and allows it to be more tightly secured to the annulus without penetrating the valve structure. A surgeon may use interrupted mattress stitching to secure the replacement valve to the annulus. Mattress stitches are chosen to allow more exact tissue to replacement valve edge approximation.
The individual sutures may be made from a 2/0 synthetic material and are fitted with curved needles at each end. The natural curve of these needles aids the surgeon in guiding the needle tips away from coronary arteries including the coronary sinus and in avoiding inadvertent penetration of the fat of the atrioventricular groove. In addition, the sutures are preferably selected, such that alternating colors of suture may be used to secure the replacement valve to the annulus. By using alternating colors of suture, the surgeon may more readily keep track of the sutures, as he or she ties them off to secure the replacement valve to the annulus. Alternating suture colors reduces the risk that the ends of discontinuous sutures will be tied together, resulting in an improperly secured replacement value and the possibility of leakage or failure of the replacement valve.
A holder may be used to position the replacement away from the annulus while the annulus is prepared to receive the replacement valve. The surgeon applies the sutures, e.g., about 18 to 24 sutures on average, such that the sutures pass through the sewing ring of the replacement valve and then through the annulus, posteriorly. Pledgets, such as compressed Teflon® felt pledgets, may be threaded separately onto the suture to strengthen the attachment of the replacement valve to the annulus. The initial pass from the posterior face of the annulus may be completed in a counterclockwise direction around the annulus. The surgeon then may pass sutures through the anterior face of the annulus and pass the suture through the sewing ring of the replacement valve. This anterior stitching may be completed in a clockwise direction. By shifting the position of the replacement valve (or the replacement valve holder) with respect to the annulus and by applying tension to the traction stitches, the surgeon may expose the annulus in the manner that facilitates the placement of securing sutures.
Once the surgeon has completed the placement of the sutures, the surgeon may place tension on the sutures and slide the replacement valve into position within the annulus. The surgeon then ties off the sutures in the order in which they were placed—first the posteriorly placed sutures followed by the anteriorly placed sutures. As each suture is tied off, the surgeon reconfirms that the replacement valve remains properly positioned and securely sealed to the annulus, so that he or she may attain a blood-tight seal between the replacement valve and the annulus.
Because of the necessity for the careful placement of the replacement valve within the annulus and the requirement that each pair of suture ends are individually tied, heart valve replacement surgery may be lengthy, requiring the patient to spend an extended period of time under anesthesia. Further, because the patient's heart must be stopped during heart valve replacement surgery, a lengthy surgery requires the patient to spend an extended period with breathing and circulation supported by a heart-lung (or heart by-pass) machine. An extended period under anesthesia and on a heart-lung machine may complicate and delay the recovery process.
In addition, as noted above, the surgeon confirms that the replacement valve remains properly positioned within the annulus after each pair of suture ends is tied, and the surgeon ensures that only continuous suture ends are tied together. Thus, the surgeon needs sufficient room to observe the suture attachment and the positioning of the replacement valve and to manipulate the sutures in close proximity to the patient's heart. This may be extremely difficult to achieve in minimally-invasive cardiac surgery (MICS), in which the surgeon may be required to operate through an opening in the patient's chest with a small diameter, e.g., between about 2 cm and about 3 cm. Further, the patient's heart may be positioned between about 10 cm and about 12 cm below the chest opening. Larger openings generally increases the risk associated with the surgery and increase the patient's recovery time. Therefore, in order to accomplish valve replacements using MICS techniques, surgeons frequently resort to a knot tying device to push the suture knots down into the patient's chest opening.